Electric vehicle and control method for electric vehicle

Abstract

An electric vehicle includes: a vehicle drive apparatus configured to receive electricity to generate vehicle drive power and to generate electricity; a secondary battery that selectively receives and outputs electricity from/to the vehicle drive apparatus; a current sensor that selectively detects (a) an electric current to be input into the secondary battery and (b) an electric current output from the secondary battery; and an electronic control unit configured to control charging and discharging of the secondary battery, and configured to calculate, using a detected value from the current sensor, an evaluation value indicating a degree of deterioration of the secondary battery due to non-uniformity in salt concentration in the secondary battery caused by charging and discharging of the secondary battery. The electronic control unit is configured to execute a capacity-raising control in which a remaining capacity of the secondary battery is raised when the evaluation value reaches a prescribed threshold.

What is claimed is: 
     
       1. An electric vehicle comprising:
 a vehicle drive apparatus configured to receive electricity to generate vehicle drive power and configured to generate electricity; 
 a secondary battery that selectively (i) receives electricity from the vehicle drive apparatus and (ii) outputs electricity to the vehicle drive apparatus; 
 a current sensor that selectively detects (a) an electric current to be input into the secondary battery and (b) an electric current output from the secondary battery; and 
 an electronic control unit configured to control charging and discharging of the secondary battery, and configured to calculate, using a detected value of the electric current from the current sensor, an evaluation value indicating a degree of deterioration of the secondary battery due to non-uniformity in salt concentration in the secondary battery caused by charging and discharging of the secondary battery, wherein 
 the evaluation value is an integrated value of damage quantities of the secondary battery, the damage quantities being calculated based on the detected value of the electric current and an energizing time of the electric current, and 
 the electronic control unit is configured to execute a capacity-raising control in which a remaining capacity of the secondary battery is raised, the capacity-raising control being executed by the electronic control unit when the evaluation value reaches a prescribed threshold. 
 
     
     
       2. The electric vehicle according to  claim 1 , wherein:
 the electronic control unit is configured to control charging and discharging of the secondary battery such that the remaining capacity approaches a prescribed target; and 
 the electronic control unit is configured to execute the capacity-raising control to raise, when the evaluation value reaches the prescribed threshold, a value of the prescribed target to a value higher than the value used when the evaluation value is lower than the prescribed threshold. 
 
     
     
       3. The electric vehicle according to  claim 1 , wherein:
 the electronic control unit is configured to control charging and discharging of the secondary battery such that the remaining capacity remains within a prescribed range; and 
 the electronic control unit is configured to execute the capacity-raising control to raise, when the evaluation value reaches the prescribed threshold, the prescribed range to a range higher than the prescribed range used when the evaluation value is lower than the prescribed threshold. 
 
     
     
       4. The electric vehicle according to  claim 3 , wherein the electronic control unit raises the prescribed range by raising at least one of a lower limit and an upper limit of the prescribed range. 
     
     
       5. The electric vehicle according to  claim 1 , wherein the vehicle drive apparatus includes an internal combustion engine, and the electric vehicle is a hybrid electric vehicle. 
     
     
       6. A control method for an electric vehicle, the electric vehicle including a vehicle drive apparatus configured to receive electricity to generate vehicle drive power and configured to generate electricity, a secondary battery that selectively (i) receives electricity from the vehicle drive apparatus and (ii) outputs electricity to the vehicle drive apparatus, and a current sensor that selectively detects (a) an electric current to be input into the secondary battery and (b) an electric current output from the secondary battery, the control method performed by the electronic control unit and comprising:
 calculating, using a detected value of the electric current from the current sensor, an evaluation value indicating a degree of deterioration of the secondary battery due to non-uniformity in salt concentration in the secondary battery caused by charging and discharging of the secondary battery; and 
 executing a capacity-raising control in which a remaining capacity of the secondary battery is raised, the capacity-raising control being executed when the evaluation value reaches a prescribed threshold, wherein 
 the evaluation value is an integrated value of damage quantities of the secondary battery, the damage quantities being calculated based on the detected value of the electric current and an energizing time of the electric current. 
 
     
     
       7. The control method according to  claim 6 , wherein:
 charging and discharging of the secondary battery is controlled such that the remaining capacity approaches a prescribed target; and 
 when the evaluation value reaches the prescribed threshold, the capacity-raising control is executed to raise a value of the prescribed target to a value higher than the value used when the evaluation value is lower than the prescribed threshold. 
 
     
     
       8. The control method according to  claim 6 , wherein:
 charging and discharging of the secondary battery is controlled such that the remaining capacity remains within a prescribed range; and 
 when the evaluation value reaches the prescribed threshold, the capacity-raising control is executed to raise the prescribed range to a range higher than the prescribed range used when the evaluation value is lower than the prescribed threshold. 
 
     
     
       9. The control method according to  claim 8 , wherein the capacity-raising control raises the prescribed range by raising at least one of a lower limit and an upper limit of the prescribed range. 
     
     
       10. The control method according to  claim 6 , wherein the vehicle drive apparatus includes an internal combustion engine, and the electric vehicle is a hybrid electric vehicle.